Ab initio investigation of topological phase transitions induced by pressure in trilayer van der Waals structures: the example of h-BN/SnTe/h-BN.

The combination of two-dimensional crystals through the formation of van der Waals bilayers, trilayers, and heterostructures has been considered a promising route to design new materials due to the possibility of tuning their properties through the control of the number of layers, alloying pressure, strain, and other tuning mechanisms. Here, we report a density functional theory study on the interlayer phonon coupling and electronic structure of the trilayer h-BN/SnTe/h-BN, and the effects of pressure on the encapsulation of this trilayer system. Our findings demonstrated the establishment of a type I junction in the system, with a trivial bandgap of 0.55 eV, which is 10 % lower than the free-standing SnTe one. The almost inert h-BN capping layers allow a topological phase transition at a pressure of 13.5 GPa, in which the system evolves from a trivial insulator to a topological insulator. In addition, with further increase of the pressure up to 35 GPa, the non-trivial energy bandgap increases up to 0.30 eV. This behavior is especially relevant to allow experimental access to topological properties of materials, since large non-trivial energy bandgaps are required.